Fixed points of the Similarity Renormalization Group and the Nuclear Many-Body Problem

The Similarity Renormalization Group reduces the off-shellness by driving the evolved interaction towards a diagonal band. We analyze the infrared limit and the corresponding on-shell interactions and its consequences for light nuclei. Using a harmonic oscillator shell model we obtain a Tjon line B(4He)= 4B(3H)-3B(2H) which can be understood from a combinatorics counting of nucleon pairs and triplets in the triton and alpha-particle and compares favorably with realistic calculations.